A rest of this type is described in patent U.S. Pat. No. 4,212,222. In this case, the arm which bears the support piece presents a downwardly turned convex cylindrical surface. To this surface are fitted two clamping pieces which are complementary to such cylindrical surface, the assembly being maintained by a single screw and nut. This construction leads to an awkward adjustment for the violinist, since he will be able to adjust the position of the support in rotation relative to the axis of the screw only in effecting rotation of such support itself. Furthermore, the adjustment in rotation is independent of the other adjustments and in particular of the inclination of the support.
A further difficulty of this known rest is that an untimely shock on the support piece loosens the nut which causes loss of the adjustment and obliges the violinist to repeat such operation. Now, such a shock may be imparted to the support during the performance of a piece of music, this naturally being completely unacceptable.
The purpose of the invention is to overcome the difficulties of the shoulder rest described in this prior document.